Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal Amount	$ 550,000	$ 565,000
Deferred Loan Fees	(5,662)	(6,088)
Carrying Value	544,338	558,912
Senior unsecured notes payable
Debt Instrument [Line Items]
Principal Amount	300,000	300,000
Deferred Loan Fees	(5,226)	(5,605)
Carrying Value	294,774	294,395
Senior unsecured term loan
Debt Instrument [Line Items]
Principal Amount	100,000	100,000
Deferred Loan Fees	(436)	(483)
Carrying Value	99,564	99,517
Unsecured revolving credit facility
Debt Instrument [Line Items]
Principal Amount	150,000	165,000
Deferred Loan Fees	0	0
Carrying Value	$ 150,000	$ 165,000